Re: [PATCH v2] sched/fair: sanitize vruntime of entity being migrated

[Dietmar Eggemann]

On 21/03/2023 11:02, Peter Zijlstra wrote:
> On Fri, Mar 17, 2023 at 05:08:10PM +0100, Vincent Guittot wrote:
>> Commit 829c1651e9c4 ("sched/fair: sanitize vruntime of entity being placed")
>> fixes an overflowing bug, but ignore a case that se->exec_start is reset
>> after a migration.
>>
>> For fixing this case, we delay the reset of se->exec_start after
>> placing the entity which se->exec_start to detect long sleeping task.
>>
>> In order to take into account a possible divergence between the clock_task
>> of 2 rqs, we increase the threshold to around 104 days.
>>
>>
>> Fixes: 829c1651e9c4 ("sched/fair: sanitize vruntime of entity being placed")
>> Signed-off-by: Zhang Qiao <zhangqiao22@xxxxxxxxxx>
>> Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
>> ---
> 
> Blergh, this just isn't going to be nice. I'll go queue this for
> sched/urgent and then we can forget about this for a little while.
> 
> Thanks!

Don't we miss setting `se->exec_start = 0` for fair task in
move_queued_task()? ( ... and __migrate_swap_task())

https://lkml.kernel.org/r/df2cccda-1550-b06b-aa74-e0f054e9fb9d@xxxxxxx